Las Vegas investigators do not believe there was another shooter in the Mandalay Bay room where Stephen Paddock opened fire on thousands of concertgoers. Police also said the suspect had no known ties to Islamic terrorism.

At a Friday press conference, Las Vegas Metropolitan Police Department Undersheriff Kevin McMahill told reporters that investigators are “very confident that there was not another shooter” in Paddock’s room.

Investigators have also reviewed “voluminous amounts of video from numerous locations,” but McMahill said that they have not “located any other person that we believe to be a suspect at this point.”

He added that investigators are also aware that the Islamic State (IS, formerly ISIS/ISIL) has claimed responsibility for the shooting, but said that they have found "no known nexus" to terrorism or connections to ISIS.

“What I cannot confirm to you today, and what we continue to investigate is, whether anybody else may have known about this incident before he carried it out,” McMahill said.

Police are working with the FBI and other partners on a “massive” investigation into every aspect of Paddock’s life “from birth to death,” McMahill said. He specifically mentioned investigators looking into Paddock’s personal life, political affiliation, social behaviors, economic situation, and any “potential radicalization that so many have claimed.”

He also added that investigators are also “keenly interested” in Paddock’s medical status, and continue to investigate that.

McMahill said that this case is very different from previous terrorist attacks or mass murder incidents, where a motive was much easier to determine. In most cases, investigators are able to determine a motive after finding a note left at the scene, searching through social media posts and telephone calls made before the incidents or mining the suspect’s computer data.

“While some of it has helped to create a better profile into the madness of this suspect, we do not, still, have a clear motive or reason why,” said McMahill.

McMahill said that investigators have also received more than 1,000 leads from the public, but warned that “rumor and supposition doesn’t help.”

Police are obligated to look into every lead and either debunk them or determine if there’s any validity to those leads. He said that true tips, however, are “imperative” to their investigation.

“We must remain focused solely on truth and fact,” McMahill said. “It’s very easy to assume.”

FBI special agent Aaron Rouse explained that law enforcement has teamed up with Clear Channel Outdoor to conduct an “information campaign, seeking true knowledge as to what happened in the events leading up to and involving this incident.”

No information is too small or insignificant. If you know something, say something. 1-800-CALLFBI (225-5324) w/info on the Oct. 1 shooting. pic.twitter.com/nLWlkyQTn9

Investigators also found Tannerite, an explosive composed of two substances, in Paddock’s car. They said that a “significant amount” of the explosive was in its “finished product,” while they also found ammonium nitrate and aluminum powder, which, when combined make the finished product of Tannerite.

However, McMahill said that they found the explosive in a condition that did not resemble an improvised explosive device (IED).

“Sorry to tell you, I don’t know what he was going to do with all of that Tannerite,” McMahill said. “I wish I did and we continue to try to find thatinformation out.”

Paddock also reportedly tried to purchase tracer rounds at a gun show in the Phoenix area in recent weeks, but the vendor did not have any to sell, a law enforcement official briefed on the investigation told CNN.

With tracer rounds, which leave an illuminated trace of its path when fired, Paddock could have been more accurate with shots in the dark.

McMahill also recognized Jesus Campos, a security guard at the Mandalay Bay, for being “absolutely critical” to police finding the location of Paddock during the shooting.

"It allows you to keep your weapon on not necessarily a specific target, but a specific area. ... There would have been a lot higher casualty rate if he had tracer rounds," Art Roderick, a former assistant director of the US Marshals Service, told CNN.

McMahill also took a moment to recognize Jesus Campos, a security guard at the Mandalay Bay, for being an "absolute hero.”

Campos was dispatched to the 32nd floor after a door alarm alerted the security team that Paddock’s door was ajar. When he went to investigate, he came under fire and was struck in the leg. He retreated and notified his dispatch about the shooter. When police arrive, McMahill said that Campos was “absolutely critical” to locating Paddock during the shooting.

“I don’t think we’ve done a good enough job recognizing him and his actions, and for that, I apologize,” McMahill said. “I can tell you that this was a remarkable effort by a brave and remarkable man.”